1. Field of the Invention
The present invention relates to systems and methods that are used to separate molecular hydrogen from a volume of gas. More particularly, the present invention is related to systems and methods that separate hydrogen from a volume of mixed gas and utilize the hydrogen as fuel for a fuel cell.
2. Prior Art Description
In industry, there are many applications for the use of ultra pure molecular hydrogen. For instance, there are many fuel cells that operate using hydrogen. The hydrogen, however, must be ultra pure. Any molecules of carbon dioxide, carbon monoxide or other contaminant gases that are received by the fuel cell cause damage to the fuel cell and decrease both the efficiency and the functional life of the fuel cell.
Commonly, purified hydrogen for use by a fuel cell is generated using a two stage process. In the first stage, hydrogen gas is separated from a source gas. For example, hydrogen can be separated from a hydrocarbon gas. However, in many common processes that produce hydrogen, the hydrogen gas produced is not pure. Rather, when hydrogen is produced, the resultant gas is often contaminated with hydrocarbons and/or other contaminants. It is for this reason that a second processing stage is used.
In the second processing stage, the separated hydrogen gas is then purified to remove lingering contaminants. In the art, ultra pure hydrogen is commonly considered to be hydrogen having purity levels of at least 99.9999%. In the prior art, one of the most common ways to purify contaminated hydrogen gas is to pass the gas through a conduit made of a hydrogen permeable material, such as palladium or a palladium alloy. As the contaminated hydrogen gas passes through the conduit, atomic hydrogen permeates through the walls of the conduit, thereby separating from the contaminants. In such prior art processes, the conduit is kept internally pressurized and is typically heated to at least three hundred degrees centigrade. Within the conduit, molecular hydrogen disassociates into atomic hydrogen on the surface of the conduit and the conduit absorbs the atomic hydrogen. The atomic hydrogen permeates through the conduit from a high pressure side of the conduit to a low pressure side of the conduit. Once at the low pressure side of the conduit, the atomic hydrogen recombines to form molecular hydrogen. The molecular hydrogen that passes through the walls of the conduit can then be collected for use. Such prior art systems are exemplified by U.S. Pat. No. 5,614,001 to Kosaka et al., entitled Hydrogen Separator, Hydrogen Separating Apparatus And Method For Manufacturing Hydrogen Separator.
In the past, fuel cells have mostly been used to power exotic devices, such as spacecraft. Accordingly, the cost of operating a two stage system for obtaining purified hydrogen is of little concern. However, if fuel cells are to be used to power more traditional devices, such as automobiles, a two stage process for obtaining purified hydrogen is highly problematic. Consider an automobile. Using a two stage system, hydrogen gas would be separated from a source gas at some processing plant. The hydrogen gas would then be shipped under pressure to gas stations for storage. The high pressure hydrogen gas would then have to be pumped into the automobile for use by a fuel cell. This fueling scenario requires pressurized tanks to be maintained both at the gas station and within the automobile. It also requires pumping lines and couplings for fueling the automobile that can hold hydrogen gas under immense pressure. The dangers and cost of refueling alone have long been deterrents to producing any vehicle that runs on hydrogen.
A long-standing need, therefore, exists for a single stage fuel processing system, wherein a traditional fuel, such as diesel, gasoline, can be pumped into the gas tank of an automobile or a ship in the ordinary manner. A fuel processing system carried within the automobile or ship will then obtain ultra pure hydrogen from traditional fuel in a single stage process that operates on an as-needed basis. The ultra pure hydrogen can then be used to power a fuel cell for the energy efficient production of electrical power.
This need is met by the present invention as described and claimed below.